Keira Knightley Strums the Guitar with Mark Ruffalo in NYC

Keira Knightley plays an impromptu concert for lucky passerbys in Washington Square Park, NYC this afternoon while filming a scene for Can A Song Save Your Life?, her latest flick co-starring Mark Ruffalo.

"It comes to a point where you think 'What kind of film can I make that will allow me to live a proper life?' and those big budget movies make it difficult," she told The Daily Star. "I do actually love blockbusters, but that decision has a lot that comes with it that I am not prepared to go with."